The present invention relates, in general, to novel (thio)(meth)acrylate monomers, preferably mono(thio)(meth)acrylate monomers, which are useful for the formulation of polymerizable compositions leading to transparent homopolymers and copolymers that are suitable for optical and ophthalmic uses.
The polymerizable compositions according to the invention allow the manufacture of moulded articles made of transparent polymer, which is preferably thermoplastic, by polymerization in moulds or by injection-moulding.
The transparent polymers obtained, which have refractive indices of medium to high value, 1.54 or more, are particularly suitable for optical and ophthalmic uses.
Among the optical uses of the polymers according to the invention, mention may be made of wave guides and optical fibres.
Among the ophthalmic uses of these polymers, mention may be made of spectacle lenses and contact lenses.
In general, novel monomers according to the present invention are functional monomers of mono(thio)(meth)acrylate or mono- and di(meth)acrylate type bearing a 5- to 8-membered heterocycle consisting of hydrogen, carbon and sulphur atoms and having at least two endocyclic sulphur atoms. Preferably, the heterocycle is 6- or 7-membered, better still 6-membered. Also preferably, the number of endocyclic sulphur atoms is 2 or 3. The heterocycle can optionally be fused with a substituted or unsubstituted C5-C8 aromatic or polycyclanic ring, preferably a C6-C7 ring.
When the heterocycle of the functional monomers according to the invention contains 2 endocyclic sulphur atoms, these endocyclic sulphur atoms are preferably in positions 1-3 or 1-4 of the heterocycle. According to the invention, the monomer is preferably also a thio(meth)acrylate monomer. Lastly, the monomers according to the invention preferably have molar masses of between 150 and 400, preferably 150 and 350 and better still between 200 and 300.
More particularly, the novel functional monomers according to the invention correspond to the formula 
in which Z represents H or CH3 (preferably CH3) and X represents O or S, and
when X represents S, Y represents a radical of formula: 
where R1 and R2 are chosen from H, alkyl radicals, preferably C1-C4 alkyl radicals and better still the CH3 radical, or alternatively R1 and R2 together form a (CH2)5 radical, and n1 is an integer from 0 to 2 inclusive, and
when X represents O, Y represents the radical (a) defined above or a radical chosen from the radicals of formulae: 
in which n2 is equal to 1 or 2, R3 represents H or an alkyl radical, preferably a C1-C4 alkyl radical and better still a CH3 radical, R4 represents H or an alkyl radical, preferably a C1-C4 alkyl radical and better still a CH3 or C2H5 radical, and R5 is a divalent radical chosen from the groups of the following formulae: 
in which:
A denotes an aryl group, preferably a C6-C12 aryl group and better still a phenyl group, or an alkyl group, preferably a C1-C6 alkyl group,
Rxe2x80x2 and Rxe2x80x3 denote, independently of each other, H, an alkyl group, preferably a C1-C6 alkyl group, aryl, preferably phenyl, or Rxe2x80x2 or Rxe2x80x3 can be a group 
where Ra is an alkylene group, preferably a C1-C6 alkylene group, in particular a xe2x80x94CH2xe2x80x94 group, and Rb is H or CH3,
n takes the values 0 or 1 and 0xe2x89xa6m (integer xe2x89xa64), and 
xe2x80x83R6 denotes H or CH3, and
Cy denotes a substituted or unsubstituted aryl ring, preferably a phenyl, tolyl or norbornyl ring.
Preferably, R5 is a divalent radical chosen from: 
The monomers according to the invention which are particularly recommended are the thio(meth)acrylate monomers corresponding to the formula (A) above in which X represents a sulphur atom and Y is a radical of formula (a).
The monomers according to the invention can be prepared by various known synthetic processes.
Among the mono(thio)(meth)acrylic monomers which are preferred according to the invention, mention may be made of the monomers of formulae: 
Among the di(meth)acrylic monomers which are preferred according to the invention, mention may be made of the monomers of formulae: 
in particular the dimethacrylate.
The remainder of the description gives various examples of the synthesis of the monomers according to the invention. 
0.2 mol of ethyl mercaptoacetate (2 eq) in 30 ml of toluene and 1 ml of concentrated sulphuric acid is introduced into a 250 ml three-necked flask equipped with a condenser.
The reaction mixture is brought to a temperature of 80xc2x0 C., followed by dropwise addition of either 0.1 mol of formaldehyde as a 36% solution in water (stabilized with methanol) in the case of the preparation of compound Ia, or 0.1 mol of acetone or cyclohexanone in the case of compounds IIIa and IVa.
After this addition, the reaction mixture is maintained at 100xc2x0 C. for 2 hours. Stirring is then continued overnight at room temperature.
The reaction mixture is concentrated under reduced pressure. The residue is taken up in dichloromethane and washed successively with 5% sodium hydroxide solution and then with water.
The organic phase is dried over sodium sulphate, filtered and then concentrated under reduced pressure.
The product thus obtained is purified by distillation under reduced pressure. 
Yield=76%. Boiling point=126xc2x0 C./0.1 mmHg. 
Yield=78% Boiling point=131xc2x0 C./0.1 mmHg. 
Yield=96% Boiling point=165xc2x0 C./0.3 mmHg.
0.1 mol (2 eq) of freshly prepared sodium methoxide is suspended in 70 ml of anhydrous ether; 0.05 mol (1 eq) of diester dissolved in 20 ml of anhydrous ether is added dropwise at room temperature. The reaction mixture is then stirred for ten hours at reflux. The reaction mixture is allowed to cool to room temperature and is then poured into a water-ice-acetic acid mixture.
The aqueous phase is extracted with twice 60 ml of ether. The ether phases are washed with dilute sodium hydrogen carbonate solution and then with water.
The organic phase is dried over sodium sulphate and concentrated under reduced pressure.
The xcex2-keto esters thus obtained are used crude in the remainder of the synthesis.
0.05 mol of xcex2-keto ester and 120 ml of 1N hydrochloric acid solution are introduced into a round-bottomed flask equipped with a condenser. The reaction mixture is maintained at 100xc2x0 C. for a minimum of 20 hours. The reaction mixture is taken up in 100 ml of ethyl acetate. The aqueous phase is neutralized with sodium hydroxide solution to pH 5.
The organic phase is then washed successively with water and then with saturated sodium chloride solution.
The organic phase is dried over sodium sulphate and then concentrated under reduced pressure.
The thiacycloalcan-3-ones thus obtained will be purified by chromatography on silica gel. 
Yield=79% relates to the preceding two steps. Melting point=101xc2x0 C. 
Yield=28% relates to the preceding two steps. Purification eluent: 9% ethyl acetate/91% petroleum ether. 
Yield=88% relates to the preceding two steps. Purification eluent: 10% ethyl acetate/90% petroleum ether.
0.05 mol (1 eq) of lithium aluminium hydride suspended in 20 ml of anhydrous tetrahydrofuran is introduced, under a nitrogen atmosphere, into a three-necked flask fitted with a condenser, a stirrer and a dropping funnel.
0.05 mol (1 eq) of the ketone obtained in step I.3, dissolved in 10 ml of tetrahydrofuran, is then added dropwise at room temperature.
After addition, the reaction mixture is refluxed for 12 hours. The solution is then allowed to cool to room temperature. The reaction mixture is cooled to 0xc2x0 C. in order to be hydrolysed with 20 ml of water.
The solution is then poured into 60 ml of 10% sulphuric acid solution. The organic phase is separated out and the aqueous phase is extracted with three times 60 ml of ether. The combined ether phases are washed successively with 50 ml of water and 50 ml of saturated sodium hydrogen carbonate solution and then dried over sodium sulphate and concentrated under reduced pressure. 
Yield=53%. Purification eluent: 20% ethyl acetate/80% petroleum ether. 
Yield=54%. Purification eluent: % ethyl acetate/% petroleum ether. 
Yield=78%. Purification eluent: % ethyl acetate/% petroleum ether.
20 mmol (1 eq) of alcohol obtained in the above step, dissolved in 60 ml of toluene, and 11 mmol (0.55 eq) of Lawesson""s reagent are introduced under a nitrogen atmosphere.
The reaction mixture is maintained at reflux for a variable period depending on the substrate.
The reaction is monitored by thin layer chromatography.
After the alcohol has disappeared, the reaction mixture is taken up in 100 ml of water and extracted with twice 50 ml of dichloromethane.
The combined organic phases are dried over sodium sulphate and then concentrated under reduced pressure.
The mercaptans thus obtained are used crude in the remainder of the synthesis. 
0.05 mol (1 eq) of alcohol obtained in step I.4, 0.05 mol (1 eq) of triethylamine and 800 ppm of hydroquinone monomethyl ether (HQME) in 300 ml of chloroform are introduced into a three-necked flask fitted with a condenser, a thermometer and a magnetic stirrer. The reaction mixture is cooled to 0xc2x0 C.; 0.055 mol (1 eq) of methacryloyl chloride dissolved in 20 ml of chloroform is then added dropwise, while maintaining the temperature at 0xc2x0 C.
After warming to room temperature, the mixture is left stirring for 48 hours.
The reaction mixture is acidified with 50 ml of 6N sulphuric acid solution and is extracted with ether. The organic phase is washed successively with 10% sodium hydrogen carbonate solution and then with saturated sodium chloride solution.
The ether phase is dried over sodium sulphate and the solvent is evaporated off.
The methacrylic compounds thus obtained are purified by chromatography on silica gel. 
Yield 32%. Purification eluent: 1% ethyl acrylate/99% petroleum ether. 
Yield=27%. Purification eluent: 2% ethyl acetate/98% petroleum ether. 
Yield=45%. Purification eluent: 1% ethyl acetate/99% petroleum ether.
65 mmol of methacrylic acid and 800 ppm of HQME in 70 ml of dichloromethane are introduced, with stirring, into a 250 ml three-necked flask. 32.5 Mmol of mercaptan obtained in step I.5 and 650 mg of dimethylaminopyridine (DMAP) (catalytic amount of 5% by mass relative to the acid) are added dropwise, at room temperature. The reaction mixture is then cooled to 0xc2x0 C. and 65 mmol of dicyclohexylcarbodiimide (DCC) are added. Stirring is continued at 0xc2x0 C. for five minutes and then at room temperature for five hours.
The reaction mixture is filtered in order to remove the dicyclohexylurea formed.
The filtrate is taken up in dichloromethane and the organic phase is washed successively with 0.5 N hydrochloric acid solution and then with 0.5 N sodium hydroxide solution. The organic phase is dried, filtered and concentrated under reduced pressure.
The methacrylic thioester thus obtained is purified by chromatography on silica gel. 
Yield=33%. Purification eluent: 2% ethyl acetate/98% petroleum ether.
This cyclization method makes it possible to obtain a series of dithiacycloalkane methacrylic monomers according to the scheme below.
The various steps in this synthesis are:
coupling of a dimercaptan with dichloroacetone,
reduction with lithium aluminium hydride in tetrahydrofuran, and
coupling of methacryloyl chloride with the alcohol obtained above. 
0.1 mol (2 eq) of freshly prepared sodium methoxide is dissolved in 20 ml of anhydrous methanol with stirring, followed by addition of 0.05 mol (1 eq) of the dimercaptan at room temperature.
In parallel, a solution of 0.05 mol (1 eq) of 1,3-dichloroacetone dissolved in about 25 ml of anhydrous ether is prepared.
These two solutions are simultaneously introduced into a three-necked flask with stirring, at room temperature and under a nitrogen atmosphere, over a period of about four hours.
At the end of the addition, the reaction mixture is poured into a water-ice-ether mixture containing 10 ml of 10% sodium hydroxide solution.
The aqueous phase is extracted with three times 40 ml of ether. The white precipitate of polymer is separated out by settling. The organic phases are combined, dried over sodium sulphate and concentrated under reduced pressure. 
Yield=64%. Purification eluent: 5% ethyl acetate/95% petroleum ether. 
Yield=31%. Purification eluent: 5% ethyl acetate/95% petroleum ether.
The procedure is the same as that for step I.4 above. 
Yield=43%. m.p.=65xc2x0 C. Purification eluent: 15% ethyl acetate/85% petroleum ether. 
Yield=30%. Purification eluent: 10% ethyl acetate/90% petroleum ether.
The procedure is the same as that in step I.5above. 
The procedure is the same as that in step I.6 above. 
Yield=69%. Purification eluent: 5% ethyl acetate/95% petroleum ether. 
Yield=23%. Purification eluent: 2% ethyl acetate/98% petroleum ether.
55 mmol of MAOC diluted in 25 ml of solvent (acetonitrile, acetone or toluene) to which 800 ppm of HQME have been added are introduced into a reactor under a nitrogen atmosphere, fitted with a thermometer and a dropping funnel. The reaction mixture is cooled to xe2x88x9210xc2x0 C. and the mixture: mercaptan from step II.3 (50 mmol)/triethylamine (55 mmol) diluted in 10 ml of solvent, is added dropwise.
Stirring is continued at the same temperature for five hours.
After filtering off the salt formed, the solvent is removed. The residue is taken up in dichioromethane and washed with 0.5 N sodium hydroxide solution; the organic phase is dried over sodium sulphate and concentrated under reduced pressure.
The methacrylic thioesters thus obtained are purified by chromatography on silica gel. 
Yield=30%. Purification eluent: 1% ethyl acetate/99% petroleum ether.
The various steps in this synthesis are:
treatment of a dihalo derivative with sodium disulphide (Na2S2) which allows the cyclic disulphide to be obtained. This method uses a phase transfer catalysis reaction;
next, coupling of methacryloyl chloride with the alcohol obtained above. 
xc2xc mol of Na2S.9H2O is dissolved in 100 ml of water in a three-necked flask fitted with a thermometer and a condenser, and this solution is brought to 40xc2x0 C. 3 sodium hydroxide pellets are then added, followed by sulphur, so as to obtain the desired Na2S2 system (8 g, xc2xc mol for n=2).
The mixture is cooled to room temperature and xc2xc mol of dibromo derivative in 100 ml of dichloromethane is then added. Tetrabutylammonium hydrogen sulphate (phase transfer catalyst) is then added (5 mol % relative to the halo derivative).
This solution is refluxed for one hour with stirring and is then cooled to room temperature over one hour. The organic phase is taken up in dichloromethane and then washed with water and finally dried over sodium sulphate. The solvent is then evaporated off under reduced pressure. The ring thus obtained is purified by chromatography on silica gel. 
Yield=77%. Purification eluent: 20% ethyl acetate/80% petroleum ether. 
Yield=95%. Purification eluent: 20% ethyl acetate/80% petroleum ether.

Yield=56%. Purification eluent: 2% ethyl acetate/98% petroleum ether. 
Yield=50%. Purification eluent: 2% ethyl acetate/98% petroleum 
5 g (36 mmol) of trithiane dissolved in 70 ml of anhydrous tetrahydrofuran are introduced into a three-necked flask under a nitrogen atmosphere. The reaction mixture is cooled to xe2x88x9230xc2x0 C., at which temperature 1.05 eq of nBuLi (1.6M as a solution in hexane) are added slowly. This step is exothermic and the reaction mixture turns yellow.
The temperature is maintained between xe2x88x9225 and xe2x88x9215xc2x0 C. for two hours thirty minutes. After this period, the trithiane should be entirely dissolved. Lastly, the reaction mixture is cooled to xe2x88x9270xc2x0 C. and the aldehyde dissolved in tetrahydrofuran is then added dropwise by syringe. The reaction mixture is stirred overnight at a temperature of between 0 and 25xc2x0 C.
Stirring is continued for a further one hour at room temperature and the reaction mixture is poured into an H2O/CCl4 mixture. The aqueous phase is extracted three times with carbon tetrachloride. The organic phases are collected and the trithiane in suspension is filtered off. The organic phase is washed three times with water and then dried, filtered and concentrated under reduced pressure. 
Yield=62%.
The procedure is the same as that in step I.6 above. 
Yield=30%. Purification eluent: 2% ethyl acetate/98% petroleum ether.

36 ml of BF3 etherate and 72 ml of glacial acetic acid in 120 ml of chloroform are introduced into a three-necked flask fitted with a condenser, a magnetic stirrer and a dropping funnel. The reaction mixture is brought to reflux and the mixture: 30 ml (0.3 mol) of propanedithiol, 29 ml of dimethoxymethane (0.33 mol) dissolved in 450 ml of chloroform, is then added dropwise. The addition is carried out slowly over a period of eight hours. The reaction mixture is allowed to return to room temperature and is then washed successively with four times 80 ml of water, twice 120 ml of 10% potassium hydroxide solution and again with twice 80 ml of water. The organic phase is dried over sodium sulphate and filtered and the solvent is then evaporated off under reduced pressure.
The solid residue is taken up in 60 ml of methanol and heated to the boiling point of the methanol. A hot filtration is carried out, the filtrate is allowed to return to room temperature and this solution is finally kept at xe2x88x9220xc2x0 C. overnight. The white crystals of dithiane are collected by filtration and dried. 
Yield=68%. Melting point=55xc2x0 C.
5 g (41.6 mmol) of dithiane dissolved in 80 ml of anhydrous tetrahydrofuran are introduced into a three-necked flask under a nitrogen atmosphere.
The reaction mixture is cooled to xe2x88x9240xc2x0 C., at which temperature 27.3 ml (43.68 mmol, 1.05 eq) of nBuLi (1.6 M as a solution in hexane) are added dropwise. The reaction medium is then stirred for two hours at a temperature of between xe2x88x9220 and xe2x88x9240xc2x0 C. After this period, the mixture is cooled to xe2x88x9270xc2x0 C. and the electrophile (aldehyde or epoxide) dissolved in the minimum amount of tetrahydrofuran is added slowly.
In the case of an aldehyde, the reaction is instantaneous. In the case of an epoxide, the reaction is monitored by thin layer chromatography.
Once the reaction is complete, the reaction mixture is hydrolysed slowly under cold conditions with water.
The aqueous phase is extracted three times with ether.
The organic phases are combined, washed three times with water and then with saturated sodium chloride solution.
The organic phases are dried over sodium sulphate and the solvent is then evaporated off under reduced pressure.
The product thus obtained is purified by chromatography on silica gel. 
Yield=96%. Purification eluent: 10% ethyl acetate/90% petroleum ether. 
Yield=98%. Purification eluent: 10% ethyl acetate/90% petroleum ether. 
Yield=88%. M.p.=73xc2x0 C. Purification eluent: 12% ethyl acetate/88% petroleum ether. 
Yield=93%. Purification eluent: 10% ethyl acetate/90% petroleum ether. 
Yield=72%. Purification eluent: 11% ethyl acetate/89% petroleum ether.
The procedure is the same as that in step I.6 above. 
Yield=52%. Purification eluent: 2% ethyl acetate/98% petroleum ether. 
Yield=56%. Purification eluent: 3% ethyl acetate/97% petroleum ether. 
Yield=48%. M.p.=97xc2x0 C. Purification eluent: 5% ethyl acetate/95% petroleum ether. 
Yield=40%. Purification eluent: 2% ethyl acetate/98% petroleum ether. 
Yield=41%. Purification eluent: 3% ethyl acetate/97% petroleum ether. 
5 g (46.2 mmol) of 1,3-propanedithiol and 46.2 mmol of aldehyde (acetaldehyde or propionaldehyde) in 60 ml of chloroform are introduced into a three-necked flask. This solution is stirred for one hour at a temperature of xe2x88x9220xc2x0 C. Next, 46.2 mmol of BF3 etherate are added slowly and the mixture is allowed to return to room temperature over fifteen hours.
The reaction mixture is washed three times with water and then with 10% potassium hydroxide solution. The organic phase is dried over sodium sulphate, filtered and then concentrated under reduced pressure. 
Yield=85%. Purification eluent: 3% ethyl acetate/97% petroleum ether. 
Yield=81%. Purification eluent: 2% ethyl acetate/98% petroleum ether.
The procedure is the same as that in step V.2 above. 
Yield=82%. Purification eluent: 9% ethyl acetate/81% petroleum ether. 
Yield=78%. Purification eluent: 9% ethyl acetate/91% petroleum ether. 
Yield=71%. 
Yield=89%.
The procedure is the same as that in step I.6 above. 
Yield=48%. Purification eluent: 1% ethyl acetate/99% petroleum ether. 
Yield=53%. Purification eluent: 4% ethyl acetate/96% petroleum ether. 
Yield=71%. nD20=1.5268 xcexdD=39.9 Purification eluent: 5% ethyl acetate/95% petroleum ether. 
Yield=14%. nD20=1.5425 xcexdD=41.7 Purification eluent: 4% ethyl acetate/96% petroleum ether.
The optical properties of the monomers synthesized above were evaluated by measuring their refractive index and their Abbe number. The various results are indicated in Table I below.

A=CH2, Ph 
n=0, 1
Rxe2x80x2, Rxe2x80x3, R=H, CH3, Ph 
46.2 mmol of propanedithiol and 46.2 mmol of hydroxy ketone in 60 ml of chloroform are introduced into a three-necked flask. This solution is stirred for 1 hour at a temperature of xe2x88x9220xc2x0 C. Next, 46.2 mmol of boron trifluoride etherate are added slowly and the mixture is allowed to return to room temperature over 12 hours.
The reaction mixture is washed three times with water and then with 10% potassium hydroxide solution. The organic phase is dried over sodium sulphate, filtered and then concentrated under reduced pressure. In the case of hydroxyphenyl ketones, the organic phase does not undergo any basic washing. The products thus obtained are purified by chromatography on silica gel. 
Yield=98%. 
Yield=98%. 
Yield=95%.
50 mmol (1 eq) of alcohol, 50 mmol (1 eq) of triethylamine and 800 ppm of HQME in 30 ml of chloroform are introduced into a three-necked flask fitted with a condenser, a thermometer and a magnetic stirrer. The reaction mixture is cooled to 0xc2x0 C.; next, 55 mmol (1.1 eq) of methacryloyl chloride dissolved in 20 ml of chloroform are added dropwise, while maintaining the temperature at 0xc2x0 C. After returning to room temperature, the mixture is left stirring for 48 hours.
The reaction mixture is acidified with 50 ml of 6N sulphuric acid solution and extracted with ether. The organic phase is washed successively with 10% sodium hydrogen carbonate solution and then with saturated sodium chloride solution. The ether phase is dried over sodium sulphate and the solvent is evaporated off. The methacrylic compounds thus obtained are purified by chromatography on silica gel. 
Yield=32%. nD20=1.5215 xcexdD=38.6 Purification eluent: 1% ethyl acetate/99% petroleum ether. 
Yield=50%. nD20=1.5742 xcexdD=30.8 Purification eluent: 4% ethyl acetate/96% petroleum ether. 
Yield=48%. m.p.=132xc2x0 C. Purification eluent: 2% ethyl acetate/98% petroleum ether.

46.2 mmol of dimercaptan and 46.2 mmol of hydroxyacetone in 60 ml of chloroform are introduced into a three-necked flask. This solution is stirred for 1 hour at a temperature of xe2x88x9220xc2x0 C. Next, 46.2 mmol of boron trifluoride etherate are added slowly and the mixture is allowed to return to room temperature over 12 hours.
The reaction mixture is washed three times with water and then with 10% potassium hydroxide solution. The organic phase is dried over sodium sulphate, filtered and then concentrated under reduced pressure. The products thus obtained are purified by chromatography on silica gel. 
Yield=quantitative. Purification eluent: 10% ethyl acetate/90% petroleum ether. 
Yield=67%.
50 mmol (1 eq) of alcohol, 50 mmol (1 eq) of triethylamine and 800 ppm of HQME in 30 ml of chloroform are introduced into a three-necked flask fitted with a condenser, a thermometer and a magnetic stirrer. The reaction mixture is cooled to 0xc2x0 C.; next, 55 mmol (1 eq) of methacryloyl chloride dissolved in 20 ml of chloroform are added dropwise, while maintaining the temperature at 0xc2x0 C. After returning to room temperature, the mixture is left stirring for 48 hours.
The reaction mixture is acidified with 50 ml of 6N sulphuric acid solution and is extracted with ether. The organic phase is washed successively with 10% sodium hydrogen carbonate solution and then with saturated sodium chloride solution. The ether phase is dried over sodium sulphate and the solvent is evaporated off. The methacrylic compounds thus obtained are purified by chromatography on silica gel. 
Yield=38%. nD20=1.5706 xcexdD=27.5 Purification eluent: 1% ethyl acetate/99% petroleum ether. 
Yield=30%. nD20=1.5294 xcexdD=37.6 Purification eluent: 1% ethyl acetate/99% petroleum ether.

The procedure is similar to that described above in V.2 and I.6.
The structures of the monomers were confirmed by NMR spectrography.
The 1H NMR spectra were recorded at 250 MHz on a Bruker AC 250 machine. The proton-decoupled 13C NMR spectra were recorded at 62.88 MHz on a Bruker AC 250 machine. The technique used is Spin Echo Fourier Transform (SEFT).
Tetramethylsilane was used as internal reference.
The thin layer chromatographies were carried out on silica plates (Kieselgel 60F254) and developed using potassium permanganate or iodine.
The mass spectra were acquired on a Hewlett-Packard 5971A machine by electron impact (ionization voltage: 70 eV) . The spectrometer is coupled to a gas chromatograph (capillary column of WCOT Fused Silica type, stationary phase: CP-Sil CB, length: 25 metes, inside diameter: 0.25 mm, film thickness: 0.12 xcexcm).
The refractive indices nD20 were measured at 20xc2x0 C. on an Abbe refractometer (ASTM-NFT 60194 model) for the sodium D line (589.3 nm).
The Abbe numbers (xcexdD) were calculated from the refractive index measurements at the following wavelengths: 480 nm (Fxe2x80x2 of cadmium), 546.1 nm (E of mercury), 589.3 nm (D of sodium), 643.8 nm (Cxe2x80x2 of cadmium). xcexdD is deduced by the formula: xcexdD=(nDxcx9c1)/(nFxe2x80x2xcx9cnCxe2x80x2)
The solvents were distilled before use:
anhydrous ether dried over Na2SO4, distilled over sodium and stored over sodium.
anhydrous tetrahydrofuran distilled over sodium in the presence of benzophenone and stored over sodium.
anhydrous acetone dried over CaCl2, distilled over KMnO4, dried over K2CO3 and stored over 4 xc3x85 molecular sieves.
anhydrous methylene chloride distilled over P2O5 and stored over 4 xc3x85 molecular sieves.
methylene chloride and ether distilled over P2O5.
methanol distilled over magnesium.
The present invention also relates to novel compounds which are useful as intermediates for the synthesis of monomers according to the invention.
More particularly, these novel compounds which are useful as synthetic intermediates are thiol compounds corresponding to the formula: 
in which R1, R2 and n1 are defined as above. Preferably, R1 and R2 both represent a hydrogen atom.
Among these novel compounds, mention may be made of the compounds of formulae: 
The present invention also relates to polymerizable compositions containing at least one functional monomer of mono(thio)(meth)acrylate or di(meth)acrylate type, preferably mono(thio)(meth)acrylate, bearing a 5- to 8-membered heterocycle consisting of hydrogen, carbon and sulphur atoms and having at least two endocyclic sulphur atoms.
The heterocycle which -is useful in the compositions according to the invention is preferably 6-membered.
Preferably also, the heterocycle of the monomer which is useful in the polymerizable compositions according to the invention contains two endocyclic sulphur atoms in positions 1-3 or 1-4 of the heterocycle.
In another recommended embodiment of the polymerizable compositions according to the invention, the heterocycle of the monomer is a 6-membered heterocycle containing three endocyclic sulphur atoms. Also, the monomers of mono(thio)(meth)acrylate type which are particularly recommended for the polymerizable compositions according to the present invention are thio(meth) acrylate monomers. Lastly, these monomers preferably have a molar mass of between 150 and 350 and better still between 200 and 300.
The monomers of mono(thio)(meth)acrylate type which are particularly recommended in the polymerizable compositions of the present invention are the monomers described above and represented by the formula (A), and most especially those for which, in formula (A), X represents a sulphur atom.
The polymerizable compositions according to the invention can comprise only one functional monomer according to the invention or a mixture thereof, or alternatively the compositions can contain a monomer or a mixture of monomers according to the invention as described above, with one or more other common monomers which can be copolymerized with the monomers of the invention, for the manufacture, by polymerization, of transparent polymers which have suitable optical and/or ophthalmic properties.
Any suitable comonomer which can be copolymerized with the monomers according to the invention can be used in the polymerizable compositions according to the invention.
Among the comonomers which can be used with the monomers of (thio)(meth)acrylate type for the polymerizable compositions according to the invention, mention may be made of mono- or polyfunctional vinyl, acrylic and methacrylic monomers.
Among the vinyl comonomers which are useful in the compositions of the present invention, mention may be made of vinyl alcohols and vinyl esters such as vinyl acetate and vinyl butyrate.
The acrylic and methacrylic comonomers can be mono- or polyfunctional alkyl(meth)acrylate comonomers and polycyclenic or aromatic mono(meth)acrylate comonomers.
Among the alkyl(meth)acrylates, mention may be made of styrene, xcex1-alkylstyrenes such as xcex1-methyl styrene, methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, isobutyl(meth)acrylate or difunctional derivatives such as butanediol dimethacrylate, or trifunctional derivatives such as trimethylolpropane trimethacrylate.
Among the polycyclenic mono(meth)acrylate comonomers, mention may be made of cyclohexyl (meth)acrylate, methylcyclohexyl(meth)acrylate, isobornyl(meth)acrylate and adamantyl(meth)acrylate.
Comonomers which may also be mentioned are aromatic mono(meth)acrylates such as phenyl (meth)acrylate, benzyl(meth)acrylate, 1-naphthyl (meth)acrylate, fluorophenyl(meth)acrylate, chlorophenyl (meth)acrylate, bromophenyl(meth)acrylate, tribromophenyl(meth)acrylate, methoxyphenyl (meth)acrylate, cyanophenyl(meth)acrylate, biphenyl (meth)acrylate, bromobenzyl(meth)acrylate, tribromobenzyl(meth) acrylate, bromobenzylethoxy(meth)acrylate, tribromobenzylethoxy(meth)acrylate and phenoxyethyl(meth)acrylate.
Among the comonomers which can be used in the compositions according to the invention, mention may also be made of allylcarbonates of linear or branched, aliphatic or aromatic, liquid polyols such as aliphatic glycol bis(allylcarbonates) or alkylenebis(allylcarbonates). Among the polyol(allylcarbonates) which can be used to prepare the transparent polymers which can be used in accordance with the invention, mention may be made of ethylene glycol bis(allylcarbonate), diethylene glycol bis (2-methallylcarbonate) , diethylene glycol bis(allylcarbonate), ethylene glycol bis(2-chloroallylcarbonate), triethylene glycol bis(allylcarbonate), 1,3-propanediol bis(allyl-carbonate), propylene glycol bis(2-ethylallyl-carbonate), 1,3-butanediol bis(allylcarbonate), 1,4-butanediol bis(2-bromoallylcarbonate), dipropylene glycol bis(allylcarbonate), trimethylene glycol bis(2-ethylallylcarbonate), pentamethylene glycol bis(allylcarbonate) and isopropylene bisphenol bis(allylcarbonate).
The comonomers which can be used in the compositions according to the invention also comprise cellulose esters such as cellulose acetate, cellulose propionate and cellulose butyrate.
Comonomers which can also be used are monomers of the polyalkylene glycol di(meth)acrylate type or aromatic di(meth)acrylate derivatives such as 2,2-bis-4-methacryloyloxypolyethoxyphenylpropane.
The comonomers which are useful in the present invention also comprise sulphur-containing compounds other than those of formula (A). These can be mono- or poly(meth)acrylates bearing one or more sulphur atoms or alternatively monothio(meth)acrylates or polythio(meth)acrylates, for example such as those described in patent application EP-273,710. Among the polythio(meth)acrylates, mention may be made of bis-2 methacryloylthioethyl sulphide and 4,4xe2x80x2-bis-methacryloylthiophenyl sulphide.
For an additional description of the comonomers which can be used in the compositions according to the invention, reference may be made to French patent No. 2,699,541.
The polymerization of the polymerizable compositions according to the invention can be carried out by any known polymerization process. The polymerization process which is particularly suitable in the present invention is photochemical polymerization. A recommended polymerization process is photochemical polymerization via ultraviolet radiation and preferably UV-A radiation. The polymerization conditions obviously depend on the monomers used in the compositions.
Such polymerization processes are described, inter alia, in patent FR-A-2,699,541.
Thus, the polymerizable compositions according to the invention generally also contain polymerization initiators, preferably photoinitiators, in proportions of from 0.001 to 5% by weight relative to the total weight of the composition, and even more preferably from 0.01 to 1%.
The photoinitiators which can be used in the polymerizable compositions according to the invention are, in particular, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenyl-1-ethanone and alkylbenzoin ethers.
The recommended photoinitiators are 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethyl-benzoyldiphenylphosphine oxide.
The polymerizable compositions according to the invention can also contain additives used conventionally in polymerizable compositions intended for moulding optical and ophthalmic articles, in particular contact lenses, in standard proportions, namely, inhibitors, dyes, UV absorbers, fragrances, deodorants, antioxidants and anti-yellowing agents.
The present invention also relates to transparent polymer compositions obtained by polymerization, and in particular by photopolymerization, of the polymerizable compositions described above.
The polymerization is carried out in a known manner, using an initial mixture containing the various monomers of the polymerizable composition and the optional adjuvants, the polymerization reaction being catalysable using catalysts such as benzoyle peroxide, cyclohexyl peroxydicarbonate, diisopropyl peroxydicarbonate or 2,2xe2x80x2-azobisbutyronitrile.
Preferably, the polymerization is a photopolymerization and, in this case, the polymerizable compositions according to the invention generally contain photoinitiators as indicated above.
Preferably also, this photopolymerization is a photopolymerization by irradiation with ultraviolet light.
The invention also relates to optical and ophthalmic articles manufactured from the transparent polymer compositions according to the invention, and in particular contact lenses.
The polymerizable compositions according to the invention can lead to the production of thermoplastic polymers. In this case, the polymerizable compositions are particularly suitable for obtaining optical and ophthalmic articles by injection-moulding (i.e. by compression, in a mould, of the polymerizable composition brought to a temperature above its glass transition temperature or to the melting point).
However, the compositions according to the invention can be used to obtain optical and ophthalmic articles by any standard moulding process.
In particular, lenses can be obtained in the final form by casting the polymerizable compositions between two moulds having the required surface geometry, followed by polymerization. A lens whose two faces are in their final state is thus obtained. Semi-finished lenses can also be manufactured having, after moulding, only one face in its final geometry, it being possible for the second face then to be surfaced as required.